docs: def get_invoices(self, limit=50, closed=False, get_all=False):
          """Gets an accounts invoices.
  
          :param int limit: Number of invoices to get back in a single call.
          :param bool closed: If True, will also get CLOSED invoices
          :param bool get_all: If True, will paginate through invoices until all have been retrieved.
          :return: Billing_Invoice
          """
          mask = "mask[invoiceTotalAmount, itemCount]"
          _filter = {
              'invoices': {
                  'createDate': {
                      'operation': 'orderBy',
                      'options': [{
                          'name': 'sort',
                          'value': ['DESC']
                      }]
                  },
                  'statusCode': {'operation': 'OPEN'},
              }
          }
          if closed:
              del _filter['invoices']['statusCode']
  
          return self.client.call('Account', 'getInvoices', mask=mask, filter=_filter, iter=get_all, limit=limit)